The present disclosure relates to a device for transmission and reception for voice or data communication applications. The device is capable of duplex operation and adapted to operate in an environment using a plurality of frequency bands. The present disclosure also relates to a communication means including a transmitter and receiver arrangement and antennas.
Certain mobile telephone applications such as UMTS require an arrangement having a transmitter and a receiver able to operate in full duplex mode, i.e. that transmitter and receiver are simultaneously active. The transmitter and the receiver use a plurality of frequency bands, each frequency band dedicated to voice and/or data transmission in one direction. In the arrangement of interest, transmission and reception may occur over multiple frequency bands, and the mobile system may be capable of operating both in half-duplex and in full-duplex modes.
Receiver sensitivity, for example signal-to-noise ratio, in a full-duplex operation is degraded by a transmit “noise” signal, i.e. unwanted signal, in the receive frequency band. A requirement in such arrangements, therefore, is to reduce transmit noise at the receiver, preferrably by attenuation to below the level of thermal noise inherent in any electronic circuitry.
A frequency band is a small portion of radio communication frequency spectrum, in which channels are aside for different telephony systems, such as GSM or UMTS. Each of these bands has a basic scheme set by ETSI which dictates how it is to be used and shared, to avoid interference and to set the protocol for compatibility of transmitters and receivers.
The power amplifier is the final amplification circuit portion adapted to drive the transmission signals destined for the antenna. A power amplifier expends silicon area, and causes power consumption. Power amplifiers may be either separate circuits, or integrated into a common substrate along with other transmitter circuitry.
Selected attenuation at the receiver is achieved by using a directional filter such as a circulator with a frequency filtering characteristic. In some cases, no low-Q filter on the output of the power amplifier is needed. A diplex filter connects the output to the antenna. Filters and power amplifiers take a lot of chip space and require many process steps in manufacturing. It is therefore desirable to reduce the number of filters, and the number of power amplifiers, while maintaining the capability of full duplex operation over multiple frequency bands.
In various aspects, the invention is defined in the independent claims. The dependent claims define various embodiments of the invention.
In one aspect of the invention, the transmitter and receiver arrangement is adapted for connection to one or more antennas, and is capable of full-duplex communication. In the transmitter and receiver arrangement the number of power amplifiers is fewer than the number of frequency bands. In an embodiment of the invention, the device is adapted for operation in a plurality of frequency bands, and comprises a wide-band tunable modulation stage adapted for providing signals over the plurality of frequency bands, a first filter, comprising frequency selective elements selective for each of the plurality of frequency bands to receive a transmission signal from the wide-band tunable modulation stage and to provide a filtered signal, and a final power amplifier stage adapted to receive the filtered signal, wherein the signal is directed from the wide-band tunable modulation stage through the first filter to the final power amplifier stage.
In an embodiment of the transmitter and receiver arrangement according to the invention the arrangement is such that there is no high-Q filter element in a transmit path between the power amplifiers and the antenna used for transmission. In an embodiment there is no filter element between the power amplifier and an antenna connection in the arrangement.
“High-Q” in this context refers to filters with a high Q factor, i.e. a high quality factor, as a dimensionless parameter that gives a measure of the ‘quality’ desired in a particular tuned circuit. An example of a high-Q filter is a Surface Acoustic Wave or SAW filter, based on a piezoelectric crystal. Other examples of high-Q filters include Bulk Acoustic Wave (BAW) filters, ceramic filters, and composite “metafilters”. A high Q, for the purposes of the description of the present invention, is understood to be typically a value well over 20.
In an embodiment the final power amplification stage has significantly less than 30 dB gain. This has the effect of reducing the need for filtering the signal at the output of the power amplifier. For example, the final power amplifier stage's gain is less than 25 dB, or even less than 20 dB, or even less than 15 dB.
An embodiment comprises a power amplifier with a gain of, for example, in the range of 10 dB. This contributes to achieving an arrangement wherein there is no high-Q filter at the output of the power amplifier. It may also permit the arrangement to do without duplex filters after the power amplification stage, which in turn has advantages of simple design, improved power efficiency, and thereby reduced cost.
In another embodiment the filter configuration comprises high-Q frequency filters preceeding the final power amplification stage. This has the advantage of reducing the requirements for filtering after the power amplification stage.
In another embodiment, a filter with directional attenuation characteristics is disposed between the transmitter and the receiver. This allows signals from the transmitter, destined for the antenna, to be separated from signals received from the antenna and destined for the receiver. In one embodiment, the filter with directional attenuation characteristics is disposed on a signal path for coupling the antenna to the transmitter and to the receiver.
Yet another embodiment features attenuation between transmitter and receiver which is achieved by using multiple narrow-band filters with directional attenuation characteristics, each adapted to operate on one or more of the frequency bands used for duplex operation.
According to another aspect of the invention, there is provided a method for duplex signal transmission and reception in mobile communication. The method includes:
operating a transmitter and receiver arrangement in a plurality of frequency bands,
amplifying the signal using power amplifiers in a final power amplifier stage of the transmitter and receiver arrangement, wherein the number power amplifiers in the final power amplifier stage is fewer than the number of frequency bands in the plurality of frequency bands, and
filtering an amplified signal using a filter configuration without high-Q frequency filters following the final power amplification stage.
By using power amplifiers in a final power amplifier stage of the transmitter and receiver arrangement, wherein the number power amplifiers in the final power amplifier stage is fewer than the number of frequency bands in the plurality of frequency bands, the method achieves performance sufficient for UMTS operation at lower power consumption. In particular, coupling of the amplified signal on the transmit signal path into a receive path is acceptably low.
By using a filter configuration without high-Q filters following the final power amplification stage, the method achieves a simpler routing of the signal path between transmitter and antenna, and lower power consumption.
In an embodiment, the method uses a circulator to achieve selective attenuation. The circulator directs a maximum of signal from the transmitter to the connection to an antenna and from the connection to the antenna to the receiver, while allowing little signal to pass from the transmitter to the receiver.
In an embodiment, the method uses multiple circulators, each adapted to a group of one or more of the frequency bands used for duplex operation. Thus, signals can be separated into groups which further reduces the incidence of signals on the transmit path from the transmitter which pass to the receiver.